1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fail_function.c: Function-based error injection
4 */
5#include <linux/error-injection.h>
6#include <linux/debugfs.h>
7#include <linux/fault-inject.h>
8#include <linux/kallsyms.h>
9#include <linux/kprobes.h>
10#include <linux/module.h>
11#include <linux/mutex.h>
12#include <linux/slab.h>
13#include <linux/uaccess.h>
14
15static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs);
16
17static void fei_post_handler(struct kprobe *kp, struct pt_regs *regs,
18 unsigned long flags)
19{
20 /*
21 * A dummy post handler is required to prohibit optimizing, because
22 * jump optimization does not support execution path overriding.
23 */
24}
25
26struct fei_attr {
27 struct list_head list;
28 struct kprobe kp;
29 unsigned long retval;
30};
31static DEFINE_MUTEX(fei_lock);
32static LIST_HEAD(fei_attr_list);
33static DECLARE_FAULT_ATTR(fei_fault_attr);
34static struct dentry *fei_debugfs_dir;
35
36static unsigned long adjust_error_retval(unsigned long addr, unsigned long retv)
37{
38 switch (get_injectable_error_type(addr)) {
39 case EI_ETYPE_NULL:
40 if (retv != 0)
41 return 0;
42 break;
43 case EI_ETYPE_ERRNO:
44 if (retv < (unsigned long)-MAX_ERRNO)
45 return (unsigned long)-EINVAL;
46 break;
47 case EI_ETYPE_ERRNO_NULL:
48 if (retv != 0 && retv < (unsigned long)-MAX_ERRNO)
49 return (unsigned long)-EINVAL;
50 break;
51 }
52
53 return retv;
54}
55
56static struct fei_attr *fei_attr_new(const char *sym, unsigned long addr)
57{
58 struct fei_attr *attr;
59
60 attr = kzalloc(sizeof(*attr), GFP_KERNEL);
61 if (attr) {
62 attr->kp.symbol_name = kstrdup(sym, GFP_KERNEL);
63 if (!attr->kp.symbol_name) {
64 kfree(attr);
65 return NULL;
66 }
67 attr->kp.pre_handler = fei_kprobe_handler;
68 attr->kp.post_handler = fei_post_handler;
69 attr->retval = adjust_error_retval(addr, 0);
70 INIT_LIST_HEAD(&attr->list);
71 }
72 return attr;
73}
74
75static void fei_attr_free(struct fei_attr *attr)
76{
77 if (attr) {
78 kfree(attr->kp.symbol_name);
79 kfree(attr);
80 }
81}
82
83static struct fei_attr *fei_attr_lookup(const char *sym)
84{
85 struct fei_attr *attr;
86
87 list_for_each_entry(attr, &fei_attr_list, list) {
88 if (!strcmp(attr->kp.symbol_name, sym))
89 return attr;
90 }
91
92 return NULL;
93}
94
95static bool fei_attr_is_valid(struct fei_attr *_attr)
96{
97 struct fei_attr *attr;
98
99 list_for_each_entry(attr, &fei_attr_list, list) {
100 if (attr == _attr)
101 return true;
102 }
103
104 return false;
105}
106
107static int fei_retval_set(void *data, u64 val)
108{
109 struct fei_attr *attr = data;
110 unsigned long retv = (unsigned long)val;
111 int err = 0;
112
113 mutex_lock(&fei_lock);
114 /*
115 * Since this operation can be done after retval file is removed,
116 * It is safer to check the attr is still valid before accessing
117 * its member.
118 */
119 if (!fei_attr_is_valid(attr)) {
120 err = -ENOENT;
121 goto out;
122 }
123
124 if (attr->kp.addr) {
125 if (adjust_error_retval((unsigned long)attr->kp.addr,
126 val) != retv)
127 err = -EINVAL;
128 }
129 if (!err)
130 attr->retval = val;
131out:
132 mutex_unlock(&fei_lock);
133
134 return err;
135}
136
137static int fei_retval_get(void *data, u64 *val)
138{
139 struct fei_attr *attr = data;
140 int err = 0;
141
142 mutex_lock(&fei_lock);
143 /* Here we also validate @attr to ensure it still exists. */
144 if (!fei_attr_is_valid(attr))
145 err = -ENOENT;
146 else
147 *val = attr->retval;
148 mutex_unlock(&fei_lock);
149
150 return err;
151}
152DEFINE_DEBUGFS_ATTRIBUTE(fei_retval_ops, fei_retval_get, fei_retval_set,
153 "%llx\n");
154
155static int fei_debugfs_add_attr(struct fei_attr *attr)
156{
157 struct dentry *dir;
158
159 dir = debugfs_create_dir(attr->kp.symbol_name, fei_debugfs_dir);
160 if (!dir)
161 return -ENOMEM;
162
163 if (!debugfs_create_file("retval", 0600, dir, attr, &fei_retval_ops)) {
164 debugfs_remove_recursive(dir);
165 return -ENOMEM;
166 }
167
168 return 0;
169}
170
171static void fei_debugfs_remove_attr(struct fei_attr *attr)
172{
173 struct dentry *dir;
174
175 dir = debugfs_lookup(attr->kp.symbol_name, fei_debugfs_dir);
176 if (dir)
177 debugfs_remove_recursive(dir);
178}
179
180static int fei_kprobe_handler(struct kprobe *kp, struct pt_regs *regs)
181{
182 struct fei_attr *attr = container_of(kp, struct fei_attr, kp);
183
184 if (should_fail(&fei_fault_attr, 1)) {
185 regs_set_return_value(regs, attr->retval);
186 override_function_with_return(regs);
187 return 1;
188 }
189
190 return 0;
191}
192NOKPROBE_SYMBOL(fei_kprobe_handler)
193
194static void *fei_seq_start(struct seq_file *m, loff_t *pos)
195{
196 mutex_lock(&fei_lock);
197 return seq_list_start(&fei_attr_list, *pos);
198}
199
200static void fei_seq_stop(struct seq_file *m, void *v)
201{
202 mutex_unlock(&fei_lock);
203}
204
205static void *fei_seq_next(struct seq_file *m, void *v, loff_t *pos)
206{
207 return seq_list_next(v, &fei_attr_list, pos);
208}
209
210static int fei_seq_show(struct seq_file *m, void *v)
211{
212 struct fei_attr *attr = list_entry(v, struct fei_attr, list);
213
214 seq_printf(m, "%pf\n", attr->kp.addr);
215 return 0;
216}
217
218static const struct seq_operations fei_seq_ops = {
219 .start = fei_seq_start,
220 .next = fei_seq_next,
221 .stop = fei_seq_stop,
222 .show = fei_seq_show,
223};
224
225static int fei_open(struct inode *inode, struct file *file)
226{
227 return seq_open(file, &fei_seq_ops);
228}
229
230static void fei_attr_remove(struct fei_attr *attr)
231{
232 fei_debugfs_remove_attr(attr);
233 unregister_kprobe(&attr->kp);
234 list_del(&attr->list);
235 fei_attr_free(attr);
236}
237
238static void fei_attr_remove_all(void)
239{
240 struct fei_attr *attr, *n;
241
242 list_for_each_entry_safe(attr, n, &fei_attr_list, list) {
243 fei_attr_remove(attr);
244 }
245}
246
247static ssize_t fei_write(struct file *file, const char __user *buffer,
248 size_t count, loff_t *ppos)
249{
250 struct fei_attr *attr;
251 unsigned long addr;
252 char *buf, *sym;
253 int ret;
254
255 /* cut off if it is too long */
256 if (count > KSYM_NAME_LEN)
257 count = KSYM_NAME_LEN;
258 buf = kmalloc(count + 1, GFP_KERNEL);
259 if (!buf)
260 return -ENOMEM;
261
262 if (copy_from_user(buf, buffer, count)) {
263 ret = -EFAULT;
264 goto out;
265 }
266 buf[count] = '\0';
267 sym = strstrip(buf);
268
269 mutex_lock(&fei_lock);
270
271 /* Writing just spaces will remove all injection points */
272 if (sym[0] == '\0') {
273 fei_attr_remove_all();
274 ret = count;
275 goto out;
276 }
277 /* Writing !function will remove one injection point */
278 if (sym[0] == '!') {
279 attr = fei_attr_lookup(sym + 1);
280 if (!attr) {
281 ret = -ENOENT;
282 goto out;
283 }
284 fei_attr_remove(attr);
285 ret = count;
286 goto out;
287 }
288
289 addr = kallsyms_lookup_name(sym);
290 if (!addr) {
291 ret = -EINVAL;
292 goto out;
293 }
294 if (!within_error_injection_list(addr)) {
295 ret = -ERANGE;
296 goto out;
297 }
298 if (fei_attr_lookup(sym)) {
299 ret = -EBUSY;
300 goto out;
301 }
302 attr = fei_attr_new(sym, addr);
303 if (!attr) {
304 ret = -ENOMEM;
305 goto out;
306 }
307
308 ret = register_kprobe(&attr->kp);
309 if (!ret)
310 ret = fei_debugfs_add_attr(attr);
311 if (ret < 0)
312 fei_attr_remove(attr);
313 else {
314 list_add_tail(&attr->list, &fei_attr_list);
315 ret = count;
316 }
317out:
318 kfree(buf);
319 mutex_unlock(&fei_lock);
320 return ret;
321}
322
323static const struct file_operations fei_ops = {
324 .open = fei_open,
325 .read = seq_read,
326 .write = fei_write,
327 .llseek = seq_lseek,
328 .release = seq_release,
329};
330
331static int __init fei_debugfs_init(void)
332{
333 struct dentry *dir;
334
335 dir = fault_create_debugfs_attr("fail_function", NULL,
336 &fei_fault_attr);
337 if (IS_ERR(dir))
338 return PTR_ERR(dir);
339
340 /* injectable attribute is just a symlink of error_inject/list */
341 if (!debugfs_create_symlink("injectable", dir,
342 "../error_injection/list"))
343 goto error;
344
345 if (!debugfs_create_file("inject", 0600, dir, NULL, &fei_ops))
346 goto error;
347
348 fei_debugfs_dir = dir;
349
350 return 0;
351error:
352 debugfs_remove_recursive(dir);
353 return -ENOMEM;
354}
355
356late_initcall(fei_debugfs_init);
357